CVE-2026-22989: Linux kernel · nfsd: check that server is running in unlock_filesystem
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 6.17.0-1021.21~24.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.17.0-1021.21~24.04.1, 6.17.0-1021.24~24.04.1, 6.17.0-41.41~24.04.1 +4
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 23 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: check that server is running in unlock_filesystem If we are trying to unlock the filesystem via an administrative interface and nfsd isn't running, it crashes the server. This happens currently because nfsd4_revoke_states() access state structures (eg., conf_id_hashtbl) that has been freed as a part of the server shutdown. [ 59.465072] Call trace: [ 59.465308] nfsd4_revoke_states+0x1b4/0x898 [nfsd] (P) [ 59.465830] write_unlock_fs+0x258/0x440 [nfsd] [ 59.466278] nfsctl_transaction_write+0xb0/0x120 [nfsd] [ 59.466780] vfs_write+0x1f0/0x938 [ 59.467088] ksys_write+0xfc/0x1f8 [ 59.467395] __arm64_sys_write+0x74/0xb8 [ 59.467746] invoke_syscall.constprop.0+0xdc/0x1e8 [ 59.468177] do_el0_svc+0x154/0x1d8 [ 59.468489] el0_svc+0x40/0xe0 [ 59.468767] el0t_64_sync_handler+0xa0/0xe8 [ 59.469138] el0t_64_sync+0x1ac/0x1b0 Ensure this can't happen by taking the nfsd_mutex and checking that the server is still up, and then holding the mutex across the call to nfsd4_revoke_states().
References
- ubuntu.com/security/CVE-2026-22989 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-22989 (opens in a new tab)
- git.kernel.org/linus/d0424066fcd294977f310964bed6f2a487fa4515 (opens in a new tab)
- git.kernel.org/stable/c/d0424066fcd294977f310964bed6f2a487fa4515 (opens in a new tab)
- git.kernel.org/stable/c/d95499900fe52f3d461ed26b7a30bebea8f12914 (opens in a new tab)
- git.kernel.org/stable/c/e06c9f6c0f554148d4921c2a15bd054260a054ac (opens in a new tab)
- ubuntu.com/security/notices/USN-8570-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8594-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8604-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8605-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8570-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8669-1 (opens in a new tab)